BORROWED FUNDS - Narrative (Details) - USD ($)				12 Months Ended
		Jul. 28, 2016	Mar. 07, 2016	Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014	May 13, 2016	Mar. 14, 2016
Debt Instrument [Line Items]
Repayments of long-term borrowed funds		$ 500,000,000		$ 8,429,000,000		$ 766,000,000	$ 6,000,000
Short-term borrowed funds				4,359,000,000		3,432,000,000
Subordinated Debt
Debt Instrument [Line Items]
Repayments of long-term borrowed funds				625,000,000		750,000,000
FHLB advances and letters of credit | Secured Debt
Debt Instrument [Line Items]
Short-term borrowed funds				13,400,000,000		11,300,000,000
FHLB advances
Debt Instrument [Line Items]
Available borrowing capacity				2,800,000,000		4,100,000,000
FRB advances
Debt Instrument [Line Items]
Available borrowing capacity				33,600,000,000
Banking Subsidiaries | 2.500% senior unsecured notes, due 2019 | Senior Unsecured Notes
Debt Instrument [Line Items]
Principal balance				$ 750,000,000					$ 750,000,000
Interest rate				2.50%	[1],[2]				2.50%
Banking Subsidiaries | 2.550% senior unsecured notes, due 2021 | Senior Unsecured Notes
Debt Instrument [Line Items]
Principal balance				$ 1,000,000,000				$ 1,000,000,000
Interest rate				2.55%	[1],[3]			2.55%
Citizens Financial Group, Inc. | 2.375% fixed rate senior unsecured debt, due 2021 | Senior Unsecured Notes
Debt Instrument [Line Items]
Principal balance		$ 350,000,000		$ 350,000,000
Interest rate		2.375%
Citizens Financial Group, Inc. | 2.375% fixed rate senior unsecured debt, due 2021 | Subordinated Debt
Debt Instrument [Line Items]
Interest rate	[4]			2.375%
Citizens Financial Group, Inc. | 4.082% fixed rate subordinated debt, due 2025 | Subordinated Debt
Debt Instrument [Line Items]
Principal balance						334,000,000
Interest rate		4.082%		4.082%	[5]
Extinguishment of debt, amount		$ 334,000,000
Citizens Financial Group, Inc. | 4.023% fixed rate subordinated debt, due 2024 | Subordinated Debt
Debt Instrument [Line Items]
Principal balance				$ 42,000,000		$ 333,000,000
Interest rate		4.023%		4.023%	[6]
Extinguishment of debt, amount		$ 166,000,000	$ 125,000,000

[1] These securities were offered under CBNA’s Global Bank Note Program dated December 1, 2014.

[2] This balance is composed of: principal balance of $750 million at December 31, 2016; impact from interest rate swaps of ($7) million and ($2) million of unamortized deferred issuance costs and discount at December 31, 2016. See Note 16 “Derivatives” for further information.

[3] This balance is composed of: principal balance of $1.0 billion at December 31, 2016; impact from interest rate swaps of ($30) million and ($5) million of unamortized deferred issuance costs and discount at December 31, 2016. See Note 16 “Derivatives” for further information.

[4] This balance is composed of: principal balance of $350 million at December 31, 2016, as well as the impact of ($2) million of unamortized deferred issuance costs and discount at December 31, 2016.

[5] This subordinated debt was retired in 2016. At December 31, 2015, this balance was composed of a principal balance of $334 million; impact from interest rate swaps of ($3) million at December 31, 2015. See Note 16 “Derivatives” for further information. On July 28, 2016, the Company repurchased $334 million of these securities.

[6] These balances are composed of: principal balance of $42 million and $333 million at December 31, 2016 and 2015, respectively, as well as the impact from interest rate swaps of zero and ($2) million at December 31, 2016 and 2015, respectively. See Note 16 “Derivatives” for further information. In addition, the Company repurchased $125 million and $166 million of these securities on March 7, 2016 and July 28, 2016, respectively.